Apparatus for roll forming workpieces



Jan. 5, 1965 E. c. HANNA ETAL APPARATUS FOR ROLL FORMING WORKPIECES 2 Sheets-Sheet 1 Filed Dec. 6, 1960 FIG 2 INVENTOR EDWARD Cl HANNA DONALD E. YOUTZ JACOB S. ROJAHN SW M.

' ATTORNEY Jan. 5, 1965 E. c. HANNA ETAL APPARATUS FOR ROLL FORMING WORKFIECES 2 Sheets-Sheet 2 Filed Dec. 6, 1960 INVENTOR EDWARD C. HANNA DONALD E. YOUTZ JACOB S. ROJAHN BY fimfiMw-m ATTORNEY United States Patent 3,164,042 APPARATUS FOR ROLL FGRMING WORKPIECES Edward C. Hanna, Blue Ridge Summit, and Donald E. Youtz and Jacob S. Rojahn, Waynesboro, Pa., assignors to Landis Machine Company, Waynesboro, Pa, a corporation of Pennsylvania Filed Dec. 6, 196i), Ser. No. 74,166

' 8 Claims. (Cl. 89-6) This invention relates to apparatus for roll forming workpieces and particularly to die heads for rolling tapered formation on pipe, conduit and the like. While the apparatus is intended to be used primarily for forming threads, it may also be used to form smooth surfaces on workpieces.

In die heads for cutting tapered threads it has been customary to provide means for causing the cutting tools or chasers to recede, that is, to move radially away from the center of the workpiece as the thread cutting operation proceeds, in exact correspondence with the degree of taper required. Many varieties of such receding mechanisms have been devised and, for the most part, they are extremely complex and expensive to manufacture and maintain.

Attempts at adapting such receding mechanisms to thread rolling heads have met with virtually no success. In general the known devices for causing the tools to recede during the thread cutting operation have proved to be too delicate for an operation such as thread rolling which develops extremely strong forces in operation. For example, in a thread rolling head such as that shown and described in United States Letters Patent No. 2,252,130 issued August 12, 1941, the heavy radial forces developed in all cold-rolling operations are transmitted from the rolling dies to a ring surrounding the die holders. As a consequence the surrounding ring is quite massive and any attempt to permit this ring to move during the rolling operation to cause the rolling dies to recede would in volve a receding mechanism of similar massive construction inasmuch as it would be required to absorb the same forces.

In practice, such as construction would not be feasible for several reasons. The size of the receding device would be disproportionate to the size of the head as a whole. The increased size and weight of the head would result in excessive overhanging weight on the end of the spindle, resulting in uneconomical wear on the spindle bearings and a rapid loss of accuracy of the machine.

Additionally, the very heavy rolling forces would quickly destroy the accuracy of the precision receding mechanism through wear.

The rolling head embodying the invention which overcomes these diificulties is so constructed that the strong radial forces induced during rolling are chiefly absorbed by members not involved in the size controlling or receding mechanism. It is an important feature of the invention that the force transmitted from the rolling dies to the receding device is not only reduced to a small fraction of the total but is transmitted in the form of a tangential, not a radial, force. Consequently, a control ringsurrounding the rolling die holders can be of minimum thickness in the radial direction.

Another feature of note is the fact that the rolling die holders are individually supported against the tangential rolling force by a plurality of identical cam grooves in the control ring. Thus the force transmitted to the cam ring is not only a small fraction of the total rolling force but is also divided a second time by the number of rolling dies being used. This correspondingly reduces the wear upon each individual cam groove.

The parts of the die head are united by a plurality of rods which pass through the front plate, the head body and the attaching flange. These add to the rigidity of the entire head, provide ample strength to key the control ring against the rolling force and contribute to the aim of creating a rolling head of minimum size and complexity and maximum rigidity and durability.

Accordingly, it is an object of the present invention to provide a roll forming head having novel mechanism for moving the rolling dies radially during'the rolling operation to generate an accurately tapered thread.

Another object is to provide'a rolling head of the above description in which a very large proportion of the radial rolling force is absorbed by members not directly involved in the taper-producing function.

It is a further object to provide a rolling head in which the rolling force transmitted to the taper-producing means is substantially entirely tangential in direction and minimal in amount.

A still further object of the invention is to provide a rolling head in which each of the rolling dies has means for individual connection to a common combined taperproducing and head-opening-and-closing means.

Another object is to provide means for a rolling head which serves simultaneously to guide the taper-producing means and to add rigidity to all parts of the head.

A further object of the invention is to create a rolling head of simple and rigid structure that is capable of rolling smooth or threaded, cylindrical or tapered surfaces with maximum precision and efiiciency and minimum wear and cost.

Other objects and advantages will be apparent from the following description of an exemplary embodiment of the invention and from the accompanying drawings, wherein: 7

FIGURE 1 is a front elevation of the new rolling head showing the rolling dies inclosed position with portions broken away to show interior details;

FIGURE 2 is a longitudinal section through the head, substantially along line 2-2 of FIGURE 1;

FIGURE 3 is a partial front elevation of the head showing the rolling dies in open position;

FIGURE 4 is a section through one of the die holders along line 4-4 of FIGURE 2;

FIGURE 5 is another section through one of the die holders, substantially along line 5-5 of FIGURE 4, with the rolling die omitted;

FIGURE 6 is a fragmentary section along line 66 of FIGURE 2; 7

FIGURE 7 is a side elevation of section; and

FIGURE 8 is a fragmentary radial section along line the head, partially in 8-8 of FIGURE 1.

As shown in FIGURE 2, the rolling head comprises a *head body-29 which is secured to an attaching flange 22 by a plurality of screws 24 (one shown) and a locating pin 26. The flange 22 may be provided with a shallow cylindrical recess 28 for centering on the rotatably driven spindle of the machine tool to which the head is to be atpermit the introduction of a mandrel, sensing device or the like from the machine. An operating ring'35 described in greater detail below, is mounted foraxial slidring movement on the head body between the head body'flange 32 and the attaching flange 22.

A plurality of, in this example four, cylindrical recesses 36 are formed in the front surface of the head body flange 32. These recesses serve to receive the rear trunholderaextend through aligned bores in the front plate '44, head body flange 32, operating ring and attaching flang'e22. Each rod 46 has a shoulder 48 in contact with the rear surface'of the head body flange 32 to prevent axial movement of the rod in one direction. The front plate 44 is held to the rods 46 by means of screws 50 threadedintothte front ends of the rods and by washers 52 covering the ends of the rods and an adjacent area of the front surface of the plate 44. In the space between the front plate 44 and the head body flange 32, the rods 46 are surrounded by spacing bushings 54 which serve to separate plate 44 and flange 32 the precise distance required to'accornmodate the die holders 4!);

As shown in FIGURES 2, '4 and 5, each holder 40 has a rectangular slot 56 on the side facing the center of the head for the reception of a rolling die 58 which usually is provided with peripheral ridges to produce threads on -'the workpiece. Each die 58 is rotatably journalled on a shaft 60 positioned in suitable aligned bores in the die holder 40, the bores and thevaxis of shaft 60 being eccentric with respect to the trunnions38 and 42. These trunnions are parallel with the axis of the head and consequently with the axis of the workpiece. The die shaft 60, however, is inclined with respect to the head axis by an amount-equal to the helix angle of the thread to be produced. As showninFIGURE 5 the walls of the slot 56 are provided with a similar inclination. Each shaft 60 isretained .in the respective die holder 40 against axial and rotary movement by a cone-pointed set screw 61, for example, disposed in'a threaded hole in the holder 43 (FIGURE 6).

Illustratedin the drawings are means for providing lubrication to the trunnions 38 and 42 and the rolling die 58. As an example'mist lubrication is used and the forward end of the headbody 20 is sealed to prevent escape- '60 to-conduct the lubricant to the bearing surfaces in the front plate'44 and the head body flange 32 which support the trunnions 38 and'42. Radially outwardly of the passages 64, the holes 62 contain condensing nozzles 72 to provide a film of lubricant between the outer surface of the head body 20 and the inner surface of the operating ring 35. Thislubrication system forms no part of the in- .vention and may be replaced by any other convenient means.

Each die h0lder40'has aheaded pin 74 or operating membertFlGURE 4') pressed in a suitable hole therein and extending outwardly beyond the circumferences of the front plate and the head body flange 32. A cam follower roller 76, having a crowned or spherical outer surface, is mounted on the pin 74 under the head thereof.

.Aspacing bushing 78 also surrounds pin 74 inwardly of the roller 76 and seated in a counterbore in the holder 4% to keep the roller 76 at its proper position axially of the pin. Sufiicient axial clearance is provided to permit the roller 76 to rotate freely.

The front portion of the operating ring 35 extends forwardly beyond the front plate 44 and is provided with cam slots 82 (FIGURE 7) in which the rollers 76 are received. The rods 46 act as keys to restrain the ring 35 against rotation relative to the head body 29 and absorb any rotational stress placed upon the operating ring 35.

A retaining ring 8 is secured to the rear end of operating ring 35 by screws 86, and forms one side of an annular groove 87 to receive the conventional operating yoke for moving the operating ring axially in well-known manner.

The amal travel of the operating ring 35 is limited at the rear by the front surface of the attaching flange 22. The position of the operating ring at the forward end of its travel may be made adjustable as shown in FIGURE 8. There is shown one of a pair of axially directed set screws 88, disposed in a threaded hole in the operating ring 35 and abutting the rear surface of the head body flange 32. Each screw 33 is held in adjusted position by a radially directed set screw 91). The retaining ring 84 is provided with openings 92 to provide access to the screws 88. Random holes, not shown, may be drilled axially through the operating ring 35 to prevent compression of air in the chamber between the operating ring and the head body flange 32.

In operation the head is mounted by means of the attaching flange 22 on a machine spindle that is rotatively driven and is capable of limited axial movement. The workpiece is held stationarily in a conventional gripping mechanism. The annular recess 87 in the operating ring 35 is engaged by the usual yoke which in this case may be connected to a fluid motor, as a hydraulic cylinder, for intermittent axial movement.

The operating ring 35 is disposed in its forward position as shown in FIGURES 2 and S. The adjusting screw 83 is employed to locate the ring 35 accurately in such position that the rolling dies 58 will define the proper diameter at the small end of the tapered workpiece. In this position each cam roller 76 will be located near the rear end of the respective cam slot 82 FIGURE 2).

The common axis of rotation of the trunnions 3S and 42, that is the center about which the die holder 4t! will rock was directed by the cam slot 82, is indicated at 95 in FIGURES 1 and 3. The axis of the shaft 66, is. the center of rotation of the rolling die 58, is indicated at 96. It will be apparent that a rocking movement of the die holder in the clockwise direction, as the structure is viewed in FIGURE 1, will shift the die center away from the center of the head. In other words the dies Will gradually recede to a larger diameter. The distance between the two centers should be such that a reasonable amount of rotation of the die holder, as from the position of FIGURE 1 to that of FIGURE 3 for example, will cause the rolling die 53 to be removed completely from engagement with the finished threads of the workpiece so that the head and workpiece can be rapidly sepr-arated axially.

Accordingly, the cam slots 82 (FIGURE 7) are inclined with respect to the axis of the head in such a way that rearward axial movement of the operating ring 35 will cause the cam follower rollers 76 and the die holders 40 to rock in the clockwise direction about the trunnion center 5 5. To begin the thread rolling operation the machine spindle is caused to rotate and is fed forward until the end of the workpiece is very close to the front edge of the rolling die holders :78. At this point the yoke controlling the operating ring 35 is stopped by external means while the axial movement of the remainder of the head is continued.

This continued axial movement of the head causes the rolling dies 58 to come into contact with the workpiece and to begin to roll a thread thereon. At the same time the relative axial movement between the operating ring 35, which is being held, and the head body 20, causes the rollers 76 to move forwardly in the cam slots 82. Consequently the die holders 40 are rocked in the clockwise direction (FIGURE 1) and the rolling dies 58 move gradually away from the center of the head and roll a tapered thread.

This movement continues until the required length of thread has been generated, at which point the cam follower roller 76 will be located in the cam slot 82 a short distance to the rear of the point 98. From the bottom of the slot 82 to the point 98 the slot is inclined at the angle required to produce the desired taper on the Workpiece. Forwardly of the point 93 the slot is inclined more sharply to rock the die holders 4t) in the same direction at a faster rate to withdraw the rolling dies 53 from the threads formed on the workpiece.

When the required length of thread has been generated the operating ring 35 is moved very quickly rearwardly to its limit position, shown in FIGURE 7, wherein the ring comes to rest against the forward surface of attaching flange 22. At this point each roller 76 occupies its forward limiting position in the cam slot 82, also shown in FIGURE 7. By this movement the die holders 49 are rocked virtually instantaneously from a closed position on the large diameter of the work to the open position of FIGURE 3 and the rolling dies 58 are removed from the threads on the workpiece. The die head can subsequently be restored to its original position by withdrawing the machine spindle axially, completing the op eration.

The very considerable stresses resulting from deforming the cold metal'of the workpiece are transmitted equally to each of the rolling dies 58. This radial force operates upon the center of the rolling die 58 since that center is preferably located to remain as close as possible to a radial line from the center of the head throughout the thread rolling operation. Therefore the rolling force tends to rotate the die holder 40 about the trunnion center 95 at a lever arm equal to the distance between the centers 95 and 96.

This tendency of the die holder 40 to rotate is transmitted through the roller 76 as a tangential force upon the operating ring 35 in accordance with the length of the lever arm from the trunnion center 95 to the point of contact between the roller '76 and the operating ring 35. Thus if said arm between roller 76 and center 95 is ten times the length of the arm between centers 95 and 96, the tangential force at 76 is only one tenth of the radial force at the center 96. If four rolling dies are used as shown, the tangential force at one roller 76 is only one fortieth of the total rolling force.

Therefore, the force to be resisted by any one cam track is not only reduced to a small fraction of the total rolling force but is transmitted to the cam track in the form (tangential) that is most easily resisted without unduly adding to the bulk thereto. That is to say, the metal of one fourth of the circumference of the operating ring 35, minus that removed by one cam slot 82, is available to support a tangential force on any one cam slot. This reduces the size of the head, minimizes wear and maintains accuracy over extremely long periods of time.

The head may also be used with advantage to form smooth surfaces, for example a smooth tapered surface on the end of a piece of tubing for a subsequent threading operation. In such case it has been found preferable to effect the rolling operation in the reverse direction. Rolling dies of the required form are disposed with their entrance sides toward the rear of the head. The head is then disposed, in open position with the entrance sides of the dies in position to engage the tube at a distance from the end thereof equal to the length of tapered surface desired. The head is then closed with each roller 76 being positioned slightly to the rear of the point 93 on its cam slot 82. The rolling operation is then eflfected by moving the head axially rearward while the work is held stationary, i.e. from the large diameter on the workpiece to the small, the cam slots 82 causing the dies 58 to close down as the operation proceeds. When the end of the tapered surface on the work is reached and just before the roller 76 reaches the bottom of the cam slot 82, the operating ring is drawn rapidly to its rear position, opening the head.

It will also be evident that cylindrical threads, etc., can be rolled simply by providing an opera-ting ring in which the cam slots 82 are parallel with the head axis over the length of the thread to be produced. With such a structure, no receding action will be imparted to the rolling dies.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment istherefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is: p

1. A head for roll forming workpiecescomprising a body adapted to be attached to a drive spindle, a plurality of die holders mounted on said body for pivotal movement about axes parallel to the axis of said body, dies mounted on the respective die holders for rotation about axes spaced from the pivotal axes of said die holders radially projecting operating members on said die holders, and means movable axially of said body displacing the outer ends of said operating members circumferentially of said body to thereby pivot each of said die holders simultaneously and equally about their respective pivotal axes to displace said dies radially of said body.

2. A head for roll forming workpieces comprising a body adapted to be attached to a drive spindle, a plurality of die holders mounted 'on said body for pivotal movement about axes parallel to the axis of said body, dies mounted on the respective die holders for rotation about axes spaced from the axes of said die holders, operating mem bers rigid with the respective die holders and extending essentially radially of said body, and means carried by said body for movement axially thereof engageable with said operating members to displace said operating members circumferentially of said body to thereby pivot each of said die holders simultaneously about their respective axes to displace said dies radially of said body.

3. A head for roll forming workpieces comprising a body adapted to be attached to a drive spindle, a plurality of die holders mounted on said body for pivotal movement about axes parallel to the axis of said body, dies mounted on the respective die holders for rotation about axes spaced from the axes of said die holders, operating members rigid with the respective die holders and extending essentially radially of said body, and an operating ring mounted on said body for sliding movement axially thereof, said operating ring having cam surfaces engageable with the respective operating members and operable upon axial movement of said ring to displace said operating members circumferentially to thereby displace said dies radially of said body.

4. A head for roll forming workpieces comprising a body adapted to be attached to a drive spindle, a plurality of die holders mounted on said body for pivotal movement about axes parallel to the axis of said body, dies mounted on the respective die holders for rotation about axes spaced from the pivotal axes of said die holders, 

1. A HEAD FOR ROLL FORMING WORKPIECES COMPRISING A BODY ADAPTED TO BE ATTACHED TO A DRIVE SPINDLE, A PLURALITY OF DIE HOLDERS MOUNTED ON SAID BODY FOR PIVOTAL MOVEMENT ABOUT AXES PARALLEL TO THE AXIS OF SAID BODY, DIES MOUNTED ON THE RESPECTIVE DIE HOLDERS FOR ROTATION ABOUT AXES SPACED FROM THE PIVOTAL AXES OF SAID DIE HOLDERS RADIALLY PROJECTING OPERATING MEMBERS ON SAID DIE HOLDERS, AND MEANS MOVABLE AXIALLY OF SAID BODY DISPLACING THE OUTER ENDS OF SAID OPERATING MEMBES CIRCUMFERENTIALLY OF SAID BODY TO THEREBY PIVOT EACH OF SAID DIE HOLDERS SIMULTANEOUSLY AND EQUALLY ABOUT THEIR RESPECTIVE PIVOTAL AXES TO DISPLACE SAID DIES RADIALLY OF SAID BODY. 